Fiber optic connector system

ABSTRACT

A fiber optic connector system may include a elliptical reflector arranged to couple light from one optical fiber to another. The elliptical reflector has two foci, one of which may correspond to an end of a first optical fiber and the other of which may correspond to an end of another optical fiber. Thus, light emitted from one fiber may be coupled to another fiber.

BACKGROUND

[0001] This invention relates generally to optical fibers and tocoupling or connecting those fibers.

[0002] As used herein, a fiber optic connector or splice opticallycouples one optical fiber, optical source or optical detector to anotheroptical fiber, optical source or optical detector. Therefore, lighttransmitted through one optical fiber is conveyed to another opticalfiber. A fiber optic coupler is a device that performs distribution oflight from one fiber into at least two other fibers or which coupleslight from several fibers into one fiber. Thus, a fiber optic coupler isalso a fiber optic connector.

[0003] A fiber optic connector may align optical fibers optically andsecure the fibers in the connector or splice. Most connectors use aferrule to align the fibers. In general, a ferrule is a tube with acentral passage which receives the fiber for connection. The fiber maybe held within the ferrule using epoxy or epoxyless connectors. Aninternal insert, for example, may grip the fiber providing the stabilityand tensile strength of epoxy. As the connector is crimped, the insertis compressed around the fiber.

[0004] In some cases, different connectors must be utilized fordifferent circumstances. For example, with fibers that are multi-mode,some particular types of connectors are utilized. Other connectors maynecessary when the fibers are single mode fibers. Moreover, in somecases, connectors may not achieve self-aligned fiber-to-fiber couplingbetween the coupled fibers. In some cases, good alignment tolerances maybe difficult to achieve.

[0005] In addition, simple end-to-end coupling techniques may not beamenable to use in multiplexers and de-multiplexers with a plurality ofinput or output fibers. Because of the end-to-end arrangement, there isno easy way to use the same connector as a coupler for multiple fibers.

[0006] Thus, there is a need for a better way to connect or coupleoptical fibers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a partial top plan view of one embodiment of the presentinvention;

[0008]FIG. 2 is an enlarged cross-sectional view taken generally alongthe line 2-2 of FIG. 1;

[0009]FIG. 3 is a partial top plan view of another embodiment of thepresent invention;

[0010]FIG. 4 is a partial top plan view of still another embodiment ofthe present invention; and

[0011]FIG. 5 is a mount diagram of a system in accordance with oneembodiment of the present invention.

DETAILED DESCRIPTION

[0012] Referring to FIG. 1, a pair of optical fibers 18 and 20 may becoupled by positioning their ends, indicated at S1 and S2, at theconjugate foci of an elliptical or ellipsoid reflector 16 in an opticalconnector 10. An input optical fiber 18 may abut an optical mount 14 atthe point S1. An output optical fiber 20 may abut the mount 14 at thepoint S2. A reflector 16 is positioned on the opposing side of theoptical mount 14.

[0013] The points S1 and S2 lie at the conjugate foci of the ellipticalreflector 16. Light emitted from the focus S1 is reflected at points R1or R2 on the reflector 16 is focused at the focus S2 at the end of thefiber 20. Thus, if optical fibers 18 and 20, with matching numericalapertures, are each positioned at one of the foci S1 or S2 of theelliptical reflector 16, any cone of rays exiting one fiber located atthe focus S1 is imaged onto the other fiber located at the focus S2.

[0014] The optical mount 14 may hold the elliptical reflector 16, and asecurement system including a securement device 30 for each opticalfiber 18 or 20. As shown in FIG. 2, a top plate 26 is clamped to thesupport 12 by a pair of securement devices 30 that may be clamps forexample. Each device 30 engages the top plate 26 and pulls it downwardlycausing an optical fiber 18 or 20 to be sandwiched between the top plate26 and the support 12 in a V-shaped groove 22.

[0015] The V-shaped groove 22 may be etched into the surface of asubstrate 28 that may be made of silicon or thermoplastic material, asexamples. The x and y alignment of the fibers 18 or 20 is controlled byplacing a fiber 18 or 20 on the V-shaped groove 22. The V-shaped groove22 is centered in alignment with the foci S1 or S2 of the reflector 16.The height of the V-shaped groove 22 is compatible with the diameter ofthe optical fiber 18 or 20 to be coupled. When a fiber 18 or 20 ispositioned in the V-shaped groove 22, the cores of the input and outputfibers 18 and 20 are at the same elevation.

[0016] The optical mount 14 provides accurate location of the inputfibers and output fibers at their respective foci S1 and S2.Additionally, the reflector 16 is held by the optical mount 14 so thatthe major axis of the reflector 16 is coincident with the fiber opticinput and output facets, and the minor axis is perpendicular to themidpoint of S1 and S2. The mount 14 may include a pair of mating halves14 a and 14 b.

[0017] In the connector 10, shown in FIG. 1, the input and output fibers18 and 20 are on the same side of the connector 10. The ellipticalreflector 16 may be a reflective ellipsoid or conic section placed onone side of the optical mount 14. The reflector 16 may be secured withepoxy around its edges to the mount 14. The elliptical reflector 16 maybe made by replication of a diamond turned master or by injectionmolding to manufacture in high volumes. Aluminum, silver, or goldcoating may be applied to the reflector 16 to create a highly reflectingsurface.

[0018] While a fixed positioning of the elliptical reflector 16 isillustrated in FIG. 1, the reflector 16 may be adjustable for precisearrangement of the reflector 16 with respect to the foci S1 and S2. Inaddition, in an embodiment in which the connector 10 is a coupler, thereflector 16 may be rotated to change the positioning of the foci S1 orS2 to distribute input light to more than one output fiber 20.

[0019] In an alternative embodiment, shown in FIG. 3, a connector 10 aincludes a pair of optical fibers 18 and 20 that are provided onopposite sides of a connector 10 a. The output fiber 20 may be orientedat 180 degrees to the input fiber 18. Similar deflecting systems may beprovided to orient the fiber 20 at any desired angle with respect to thefiber 18 so that the receiving cone of the fiber 20 matches thenumerical aperture of the fiber 18.

[0020] A planar, highly reflective surface 24 provides the reflection toredirect the rays from the focus S2 to the translated foci S2′. Thesurface of the reflector 24 may be made of aluminum, gold or silver tobe highly reflective. The focus S2 that would have been associated witha fiber shown in dashed lines, may be redirected to the position S2′ bythe intervention of the reflector 24. Except for the orientation of thefibers 18 and 20 with respect to one another, the connector 10 a worksin the same fashion as described previously with respect to theconnector 10.

[0021] Advantageously, the reflective surface of the reflector 16 ishighly reflective to minimize losses. Fiber separation may be controlledprecisely for 1:1 imaging. Again, the numerical apertures of the fibers18 and 20 are advantageously matched.

[0022] In the connectors 10 and 10 a shown in FIGS. 1 through 3,self-aligned fiber-to-fiber coupling may be achieved due to 1:1 imagingfrom the reflector 16. Low to moderate cost may be achieved in someembodiments due to the fact that the pieces needed to produce theconnector 10 or 10 a can be mass-produced. Imaging conditions areachromatic. Good alignment tolerances may be readily achieved. The sameconnector 10 or 10 a may be used in single mode, and multi-mode fibers.The stringent alignment tolerances of single mode system may beaccommodated.

[0023] A coupler 10 b, shown in FIG. 4, may receive an input on theoptical fiber 18 and provide an output on the optical fibers 20 and 32in accordance with one embodiment of the present invention. Of course,the number of output fibers may be any desired number. Similarly, inputsignals may be provided on the optical fibers 20 and 32 and an outputmay be provided on the optical fiber 18.

[0024] Light incident through the focus S1 is reflected by theelliptical reflector 16 onto a dispersive element 34. The dispersiveelement 34 focuses the incident light on two spaced foci S2′ and S3′each associated with an end of one of the optical fibers 20 and 32. Thedispersive element 34, that may be a reflective grating or a prism,creates or contributes to the creation of multiple foci.

[0025] In some embodiments, the dispersive element 34 may produce morethan two foci as mentioned previously. In addition, the dispersiveelement 34 may work in both directions. Thus, if light is incident onthe fiber 18, the element 34 works as illustrated in FIG. 4. However, iflight is incident through the optical fibers 20 and 32, the element 34focuses both light sources on the focus S1. Thus, the coupler 10 b isbi-directional.

[0026] The equation shown below governs the choice of the onedimensional grating pitch, angle of incidence, and angle of diffractionand the spacing between the output and input optical fibers in anembodiment in which the element 34 is a reflective grating:

mλ=d[sin Θ_(i)−sin Θ_(o)]

[0027] where m is the order of diffraction, d is the grating period,Θ_(i) is the angle of incidence normal to the surface of the reflectivegrating and Θ_(o) is the diffracted output angle with respect to normal.The order of diffraction may be plus one or minus one or higher orders.

[0028] Normally, couplers such as the coupler 10 b used for wavelengthdivision multiplexing operate in the wavelength from fifteen hundredthirty nanometers to fifteen hundred sixty-five nanometers. The channelspacing is generally one hundred gigahertz. Four, eight, sixteen orthirty-two channels may be located on the one hundred gigahertz channelgrid.

[0029] The other components of the coupler 10 b are as describedpreviously in connection with FIGS. 1-3. Instead of simply clamping onefiber, one securement device 30 may be utilized to clamp two or morefibers on a substrate 28.

[0030] The coupler 10 b may be utilized as a multiplexer 10 b ₁ and ade-multiplexer 10 b ₂ of a wavelength division multiplexer (WDM) system.Multiplexers are devices which are able to launch, on the same opticalfiber, two or more signals with different wavelengths that are thenseparated at the output end of the fiber by a de-multiplexer. Themultiplexers and de-multiplexers are reciprocal devices. That is, thesame coupler can be utilized as either a multiplexer (N:1) orde-multiplexer (1:N). The only difference between a coupler used as ade-multiplexer and a coupler used as a multiplexer may be theperformance required for isolation.

[0031] For example, a four channel WDM system may use a WDM multiplexerthat combines four independent data streams, each of a unique wavelengthgenerated by one of the four generators 36 shown in FIG. 5. The WDMmultiplexer 10 b ₁ creates four output data channels over a single line42. Each channel carries light of a different wavelength λ1-λ4. Theerbium-doped fiber amplifier 38 compensates for fiber losses. Awavelength addition or dropping unit 40 may be situated on the line 42together with an additional preamplifier 38. The unit 40 allows achannel to be added or removed. The de-multiplexer 10 b ₂ at the fiberreceiving end separates out the four data streams λ1-λ4 on the singleline 42. The light detectors 44 may convert light energy into electricalsignals.

[0032] Thus, by allowing multiple WDM channels to coexist on a singlefiber, one can tap into the huge fiber bandwidth with data ratesexceeding several tens of gigabits per second. Embodiments of thepresent invention may implement a passive reflective coupler. The use ofa passive reflective coupler may obviate the need for fused fibercoupling designs or two by two cascaded fiber coupling designs. Thelatter two designs may have a larger insertion loss. Assembly, in someembodiments of the present invention, may be simple with only threemajor pieces, the fibers on the V-shaped grooves 22, the optical mountwith the and the elliptical reflector 16. Alignment features or marksmay be provided on the optical mount 14 and the V-shaped groove 22 forautomated assembly. The elliptical reflector's focal length anddispersive element power may be designed such that the output anglesmatch standard fiber pitches.

[0033] While the present invention has been described with respect to alimited number of embodiments, those skilled in the art will appreciatenumerous modifications and variations therefrom. It is intended that theappended claims cover all such modifications and variations as fallwithin the true spirit and scope of this present invention.

What is claimed is:
 1. A fiber optic connector comprising: a mount; asecurement system to secure at least two optical fibers to said mount;and an elliptical reflector, secured to said mount, to couple light fromone of said fibers to the other of said fibers.
 2. The connector ofclaim 1 wherein said securement system includes clamps, each clampclamping an optical fiber onto said mount.
 3. The connector of claim 2wherein said mount includes a V-shaped groove to receive said fiber. 4.The connector of claim 1 wherein said connector includes a fiber havingan end and said mount includes an optical mount, said optical mountpositioned to act as a stop for the end of said fiber secured in saidsecurement device.
 5. The connector of claim 4 wherein said connectorincludes a pair of fibers having ends and said optical mount is coupledto said reflector and abuts the ends of said pair of fibers secured insaid securement device.
 6. The connector of claim 1 wherein saidelliptical reflector has a pair of foci, and said connector includes apair of stops for two fibers positioned on said mount, said focicorresponding to said stops.
 7. The connector of claim 1 wherein saidmount has two opposed sides, said connector including a pair ofsecurement devices on the same side of said mount.
 8. The connector ofclaim 1 wherein said mount has two opposed sides, said connectorincluding a pair of securement devices each on one of the opposite sidesof said mount.
 9. The connector of claim 1 wherein said ellipticalreflector includes a pair of foci, said connector further including aplanar reflector arranged to reposition one of said foci.
 10. Theconnector of claim 1 including a securement device to secure at leastthree fibers on said mount, said connector further including adispersive element to disperse light reflected by said ellipticalreflector and to form two foci.
 11. The connector of claim 10 includingan optical mount arranged to form a stop for at least three opticalfibers, the optical mount arranged to position the ends of said opticalfibers at the three foci formed by the combination of said ellipticalreflector and said dispersive element.
 12. The connector of claim 11wherein said dispersive element is a reflective grating.
 13. A method ofconnecting optical fibers comprising: arranging a pair of optical fiberswith their ends proximate to one of two foci of an elliptical reflector;and causing light emitted from one of said optical fibers to bereflected by said elliptical reflector to the end of the other of saidoptical fibers.
 14. The method of claim 13 including securing each ofsaid optical fibers on a mount.
 15. The method of claim 14 includingclamping each of said fibers onto said mount.
 16. The method of claim 15including clamping each of said fibers into a V-shaped groove in saidmount.
 17. The method of claim 13 including aligning each of said fiberends with said foci of said elliptical reflector.
 18. The method ofclaim 13 including reflecting light reflected by said reflector toreposition one of the foci of said elliptical reflector.
 19. The methodof claim 18 including reflecting the light reflected by said reflectorto position the foci on opposite sides of said reflector.
 20. The methodof claim 13 including dispersing light reflected by said reflector toform two foci from said light reflected from said reflector.
 21. Themethod of claim 20 including positioning an optical fiber at each ofsaid foci formed from the dispersed light reflected from said reflector.22. The method of claim 21 including reflecting said light from agrating after causing the light to reflect from said ellipticalreflector.
 23. The method of claim 13 including coupling light receivedfrom a first optical fiber and reflected by said reflector to at leasttwo optical fibers.
 24. The method of claim 13 including coupling lightreceived from at least two optical fibers to said elliptical reflectorand focusing said light from said elliptical reflector on a singleoptical fiber.
 25. The method of claim 13 including multiplexing lightfrom a plurality of light generators each of a different wavelength,transmitting a combined light signal over a line to a demultiplexer anddemultiplexing said light into a plurality of signals of differentwavelengths.
 26. A wavelength division multiplexing system comprising: amultiplexer coupled to a plurality of input lines; a first output linecoupled to said multiplexer; a demultiplexer coupled to said firstoutput line, said demultiplexer further coupled to a plurality of secondoutput lines; and said mutliplexer including an elliptical reflectorthat distributes light from said input lines to said first output line.27. The system of claim 26 wherein said demultiplexer includes anelliptical reflector that distributes light from said first output lineto said plurality of second output lines.
 28. The system of claim 26wherein said multiplexer includes a dispersive element which receiveslight from said first input lines reflects said light toward saidelliptical reflector to focus said light on said first output line. 29.The system of claim 26 wherein said demultiplexer includes a dispersiveelement, said dispersive element arranged to receive reflected lightfrom said elliptical reflector and to produce a plurality of outputlight beams on said second output lines.
 30. The system of claim 28wherein said dispersive element is a reflective grating.